Electrolytic process for the preparation of printing cylinders



Patented Oct. 8, 1940 UNITED STATES PATENT OFFICE Irving Gurwick, MountVernon, and Robert A.

Jennings, Pleasant Township,

Knox County,

Ohio, assignors to Shellmar Products Company,

Mount Vernon,

Ohio, a corporation of Delaware Application July 16, 1936, Serial No.90,848

3 claims. A

The present invention relates to the production of printing cylindersfor use in the intaglio printing of materials such as transparentcellulose sheeting.

A principal object of the present invention is the provision of an ironsurfaced intaglio printing cylinder in which the image desired to beprinted is etched directly into the iron.

An additional object is to provide an improved intaglio printingcylinder and the method of providing the same whereby excellent resultsare obtained from the standpoint of depositing a satisfactory image andthe cylinder will stand up for considerably longer periods of use thanthe cylinders known heretofore.

Still another object is to provide an intaglio printing cylinder havinga seamless steel base and an image-receiving outer surface composed ofelectrolytic iron integrally bonded to the base.

These and other objects will be observed upon a consideration of thefollowing specification of a preferred embodiment of the invention andby reference to the accompanying drawing in which the single figure is across sectional view of a printing cylinder constructed in accordancewith the present invention.

In the production of the cylinder a standard cold rolled shaft l is cutto the desired dimensions and the end plugs l l are forced into aseamless mild steel tube l2, the latter having a carbon content of 0.15per cent or lower. The tubing preferably is of the hot rolled type andof uniform dimensions. The thickness of the seamless steel tube may beof the order of ve-sixteenths inch and a diameter is chosen which Willbe about 0.05 inch oversize.

The plugs H are properly secured to the shaft l0 as by suitable pins.After the rough cylinder resulting from the above described procedure isproduced, the shaft l0 is mounted in a lathe between centers and isturned by a high speed cutting tool down to a final diameter slightlyless than the diameter of the printing cylinder. Thereafter the cylinderis mounted in a lathe having journaled bearings and again is turnedto asomewhat accurate and smooth outer surface. We have found that theaccuracy required in the operation makes .it highlydesirable to employfor the second turning operation a lathe having journaled bearingsrather than a center mounting.

Thereafter, the steel cylinder is given a fine nish by grinding with asuitable stone. The grinding operation is followed by a polishingoperation Which may be effected with a carborundum cloth or the like. Inview of the particular nature of the metal and the previous operationsthis polishing generally can be accomplished in fteen or twenty minutes.

The polished cylinder is cleaned thoroughly with a solution which mayinclude sodium cyf anide, salt and hydrochloric acid. Special bushingsfor plating are mounted on the ends of the shaft I0 and the cylinder issubjected to an operation for the electrolytic disposition of ironthereon, the ends of the cylinder being painted with a resistant lacquerwhich will prevent the disposition of metal thereon. Such lacquers arewell known in the plating art.

The solution employed in plating the cylinder may vary to some extent.One solution which has proven satisfactory is composed of 30% FeClzAHzO35% CaClz (Anhydrous) 35% H20.

It has been found that a technical grade of chemicals free of nickel,arsenic andl lead may be employed for the plating solution, therebyconsiderably reducing the expense of the plating operation. A

The solution is supersaturated at ordinary temperatures and the platingbath is maintained at a temperature of the order of 200 to 210 F. as bya suitable steam jacket. It is preferred that the plating tank becomposed of a material such as ceramic tile or Portland cement. For theanode plates scrap iron, sheet steel or the like may be employed, itbeing necessary to separate the anode from the cylinder which forms thecathode as by suspending the plates in a porous ceramic pot,

The cylinder rst is mounted in the plating bath with about one-third itscircumference immersed. Rotation is imparted to the cylinde.y and theplating operation is carried on until an electrolytic deposition of ironof suitable thickness is obtained. 'Ihis may require a `time of theorder of 1 to 3 hours, depending upon the thickness desired. The currentdensity may be 21/2 to 3 45 amperes per square inch of total surface ofa cylinder and the voltage may be 12 to 15. In general, higher currentdensities are employed since these result in a more dense deposit. Insome cases a current of 20 volts and 51/2 amperes 50 has been employedto obtain a very hard surface.

/The plating process is accompanied by the formation of impurities whichare kept away from contact with the cylinder. It has been found thatWhere a current of 12 volts and 3 amperes is em- 55 ployed in theplating and the operation is continued for 1 hour there will result adeposit of approximately 0.003 inch.

The plated. surface is quite smooth, coherent and tough. It is free fromimperfections and the entire coating is integrally connected to the basecylinder. This outer coating is indicated in the drawing at I3. It ispreferred that the coating have a thickness of the order of 0.005 whichmay require a plating time of around 2 hours. The finish of the surfaceof the cylinder can be controlled to a considerable extent bycontrolling the rate of rotation of the cylinder in the plating bath,that is, as a general rule rotation at a relatively high peripheralspeed results in a smoother finish than rotation at lower speeds. In oneinstance we have employed a peripheral speed of the order of 200 feetper minute, but higherspeeds may be utilized to advantage..

As before stated, the plating bath is hot and after the platingoperation is completed the cylinder is withdrawn from the bath andcooled sufficiently gradually to prevent buckling or warping of thecylinder. In order to prevent further action of the chemicals on thecylinder the latter promptly is washed with hot Water after removal fromthe plating bath. The cylinder may be cooled by gradually reducing thetemperature of the wash water so that a time of the order of one-halfhour is consumed in bringing the temperature of the cylinder down tonormal. One desirable way of cooling the cylinder is to immerse it intoa bath of hot water and to allow the Water to cool to room temperatureor thereabouts.

After the cylinder is properly .cooled it is mounted on a lathe and handpolished with a polishing cloth. This operation may require a time ofthe order of three-quarters of an hour.

The finish of the electrolytic iron is better than the finish of thecopper shells employed heretofore for intaglio cylinders and the ironsurface is a good deal harder than the copper.

After cleaning the cylinder with a mixture of pumice and 28 per centacetic acid the cylinder is mounted in a transfer machine. sensitizedcarbon tissue, exposed behind an opaque negatitve or design for a timewhich may be of the order of one-half longer than would be necessary forthe production of a copper etched cylinder and thereafter, is mounted ona zinc plate coated with a rubber cement. The tissue then is transferredto the electrolytic iron surface of the plating cylinder in the usualmanner. The ,cylinder then is immersed in Water at around 115 F. andsoaked for one-half hour, the paper backing for the tissue beingremoved. After removing the excess gelatin the cylinder is Washed withalcohol and dried. Thereafter a high grade acid-proof paint is placed onthe portions of the cylinder not to be etched, two coats of the paintbeing preferred. The cylinder then is subjected to an etching process inwhich the cylinder is placed in a solution consisting of a mixture offerrous chloride and ferrous sulphate of about 40 B. density at 60 F.About 2% pounds of anhydrous calcium chloride is added to gallons of thesolution. It is preferred that the solution be cooled to 60 F. by theaddition thereto of solid carbon dioxide.

'We have found that the solution may be stabilized and that the calciumchloride will dissolve more readily where small quantities of strontiumchloride or lithium chloride or equivalent compounds are employed in thesolution.

The amounts of these'materials added to the solution may be 20 grams tof4 pound, 2 or 3 ounces generally being employed.

The etching is effected electrolytically. A. cylindrical sheet ironanode having a diameter of some 2 inches more than the diameter of thecylinder to be etched is employed, the printing cylinder beingconcentrically mounted within the anode. A 6-volt storage battery may beemployed to provide a steady current, the battery being of the typesupplying 20 amperes. Before the current is turned on the cylinder isrevolved around in the etching solution to open the tissue. Thisprocedure may require some fifteen or twenty mintues. Thereafter, thecurrent is turned on u ntil the color in the bottom of the cells issomewha'white. The current then is turned off and rotation of thecylinder continued until the cells again become green. Some-10 orminutes may be required for the latter change. The current then isrenewed at a decreased de nsity until the cells again become white.'I'he electrolytic process is carried just to the point Where the carbontissue begins to break down. This is evidenced frequently by a wrinklingeffect. The cylinder then is removed from the solution and immediatelywashed with Water to remove the etching solution.

After cleaning the remains of the tissue from the cylinder the latter isready for use. The etching process is sufficient to dissolve the etchedmetal to a depth which provides adequate inkcarrying capacity and thecell structure of the etched portion is particularly stable.

The electrolytic iron, of which the outer surface of the cylinder iscomposed, is resistant to atmospheric corrosion and the wear thatprinting cylinders of this type encounter. Additionally, the cylinderdoes not have a tendency to receive scratches upon its surface. In usethe cylinder will last for a considerably greater period of time thanthe cylinders known heretofore.

In a preferred embodiment of the invention the iron plated cylinder isprovided with a ash of chromium. The chromium has a further preservingeffect upon the iron and is more unctuous. 'Ihe latter characteristic isof particular benefit since the cylinder is used in connection with adoctor blade which scrapes the ink from the portions of the .cylinderwhich are not etched. To provide the flash of chromium, the cylinder maybe immersed in a chromium plating bath and subjected to a platingcurrent of 1 ampere per square inch at 4 to 6 volts. Ten minutes platingtime generally is suflicient to provide the thin coat of chromium. Thetemperature of the bath is approximately 110 F. and after the chromiumplating procedure the plated cylinder is immersed in a bath of water at110 F. and allowed to remain over night to anneal the iron underneaththe chrome plate, the iron plate being very sensitive to temperaturechanges.

By providing an iron base for the flash of chromium the latter is muchless liable to be damaged than where the chromium is employed inconnection with a soft metal base composed of copper or the like. Theiron may have a hardness of 200, as indicated by the Brinnel test, whilethe copper coating will have a hardness of the order of 25 on theBrinnel scale. The chromium is integral with theelectrolyticallydisposed iron layer and the latter is integral with thelbase member. This construction is of parstands up under the actionticular utility where long runs of a particular design are to be made.The etched portion of the doctor blade for substantial periods Withoutthe destruction of the cell structure. Additionally, the unetchedportions of the cylinder remain perfectly smooth so that the doctorblade wipes such portions clean.

The amount of chromium is quite small, preferably being just enough toimprove the wiping characteristics of the cylinder.

We have found that the improved cylinder is of particular utility in theproduction of cylinders for `printing tone, etches, highlights anddelicate patterns. In addition to the improved characteristics of thecylinder from the standpoint of the printing operation, the cylindersmay be produced at a considerably lower cost than the cylinders knownheretofore. The 'time required for producing the cylinders is somewhatshorter than has been required heretofore so that quicker deliveries ofthe printed matter now are possible.

Transparent cellulose sheeting has been recognized as being quitedifficult to print, but the improved cylinders described herein producea sharp and Well defined image upon such materials. Lacquer inks may beused with the cylinders in standard gravure machines. The improvedprinting qualities may be due in part to the resistance of the etchediron cylinder to wear. Copper based cylinders have a tendency to attenso that the bottom of the etched portion comes up to an extentsuflicient to counteract the doctor blade. This does not occur in ourimproved cylinder.

The specic composition of the plating and etching baths obviously may bevaried, as may the plating procedure. It may be found desirable in somecases to provide the base member with a coating of a material which willallow the deposit of the electrolytic iron and prevent the latter lfrombecoming integrally bonded thereto. Where the integral bond is obtainedand it is desired to reuse the cylinder, the electrolytically depositediron is ground from the base member to an extent sufficient to removethe etched surface and the base cylinder again is polished and 3subjected to an iron plating step which will renew the electrolytic ironlayer.

The various changes which may be made without departing from the scopeofthe invention are intended to be included in the appended claims.

I claim:

1. The method of forming intaglio printing cylinders, which comprisesproviding a steel basei cylinder of a uniform diameter slightly lessthan the desired diameter, polishing said steel cylinder to obtain .asmooth surface, electrodepositing over said surface an even densecoating of a thickness between about 0.003 to about 0.005 inch of ironby rapidly moving said cylinder in the electrolyte while maintaining ahigh current density, polishing said iron surface, and subjecting theiron surface to an etching process.

2. The method of forming intaglio printing cylinders, which comprisesproviding a steel base` cylinder, smoothing the surface of saidcylinder, electrodepositing over said surface an even dense coating of athickness of about 0.003 to about 0.005 inch of iron by rapidly movingsaid cylinder in the electrolyte while maintaining a high currentdensity, polishing the resulting layer of iron,

subjecting the polished cylinder to an electrolytic process for etchinga desired design, and subjecting the etched cylinder to the chromiumplating process for depositing a thin coating of chromium thereon.

3. The method of forming intaglio printing cylinders, which comprisesproviding a shaft member, mounting a seamless steel tube about saidshaft member, said tube having a diameter slightly greater than desired,subjecting said tube to a turning, grinding and polishing operation toprovide a smooth nish therefor, clcctrodepositing on said tube an evendense coating of a thickness of between about 0.003 to about 0.005 inchof iron byrrapidly moving said cylinder in the electrolyte whilemaintaining a high current density, polishing said iron, subjecting thepolished iron to an etching process for producing a design thereon, anddepositing of electrolytic chromium thereon.

IRVING GURWICK. ROBERT A. JENNINGS.

a light coating Y

